The human skeleton is composed of 206 bones that perform a variety of important functions, including support, movement, protection, storage of minerals, and formation of blood cells, among others. Among these bones, the long bones (e.g., the femur, tibia, and fibula of the legs; and the humerus, radius, and ulna of the arms, among others) provide structural limb support and enable movement and locomotion. To ensure that the long bones retain their ability to perform these functions, and to reduce pain and disfigurement, long bones that are fractured or otherwise compromised should be repaired promptly and properly.
Fractured bones typically are treated using fixation devices. These devices reinforce the bone around the fracture and keep the bone aligned during healing. Fixation devices may take a variety of forms, including casts for external fixation, and bone plates, bone screws, wires, and/or rods for internal fixation. For example, to treat a more severely fractured long bone, it may be necessary or desirable to fix fragments of the bone using an intramedullary rod received in the medullary canal of the bone to stabilize the fragments.
The installation of an intramedullary rod in a fractured long bone generally involves enlargement of the bone's medullary canal with a reamer so that the rod fits into the canal. A standard procedure involves use of a guide wire, as follows. First, an entry hole that communicates with the medullary canal of the long bone may be formed near an end of the long bone. Second, a guide wire may be inserted through the entry hole and into the canal, so that the guide wire extends along the length of the canal. Third, a cannulated reamer (a “wire-guided” reamer) then may be placed over the guide wire, allowing the reamer to slide along the guide wire as the reamer widens regions of the medullary canal. Finally, after reaming is completed, a suitable intramedullary rod may be inserted into the widened canal and secured to the bone (e.g., using bone screws).
Wire-guided bone reamers may have several disadvantages. For example, wire-guided reamers may be difficult to clean and sterilize. In addition, these reamers must have a shaft diameter substantially greater than that of the guide wire, leaving less room around the shaft in the reamed canal for bone debris to accumulate. Consequently, bone debris may be packed ahead of these reamers as they ream bone, resulting in increased pressure, which may damage bone and/or create embolisms that obstruct blood flow. Additional disadvantages of wire-guided reamers involve the use of a guide wire. In particular, the guide wire, to be received by wire-guided reamers, should be thin. A guide wire that is thin may be challenging to feed past fracture sites and may be too flexible to aid in fracture reduction. Furthermore, insertion (and optional retrieval) of any guide wire increases surgical time during installation of an intramedullary rod.